Nuclear receptors constitute a large family of transcription factors that control development and homeostasis of complex organisms, and play fundamental roles in human diseases. In contrast to classic steroid and thyroid hormone receptors, orphan nuclear receptors were originally identified without any prior knowledge of their association with natural or synthetic ligands. Studies of orphan nuclear receptors has not only led to the discovery of new hormone response systems and regulatory pathways controlling cell fate, organogenesis and vital metabolic functions, but also helped in uncovering molecular mechanisms common to the action of all members of the nuclear receptor family. This meeting will demonstrate the importance of orphan nuclear receptors in health and diseases, their potential as targets for drug discovery and the distinction and likeness in the molecular mechanisms of action used by orphan and steroid nuclear receptors. Nuclear receptors are proteins that communicate to the cells information carried by small lipid-like molecules such as steroid hormones, vitamin A and D, fatty acids and prostaglandins. These receptors control normal embryonic development and physiological functions, but have also been implicated in numerous diseases such as diabetes, atherosclerosis, obesity and cancers. As nuclear receptors have proven to be excellent targets for drug discovery, it is expected that the results discussed at this meeting will have a direct impact on the treatment of these and numerous other human diseases.